Tobacco companies have developed and implemented advertising and marketing efforts to reduce perceptions of harm associated with tobacco use, increase perceptions that tobacco is socially acceptable, and encourage and sustain use of tobacco. Many marketing strategies have particulariy focused on adolescents and young adults. There are gaps in the science concerning 1) how perceptions influence tobacco use among adolescents and young adults, including changes in patterns of tobacco use from initiation to regular use, cessation, relapse, product switching, or dual use; 2) the role of pro- and anti- tobacco messages on perceptions of new tobacco products such as e-cigarettes, cigarillos, smokeless tobacco, snus, dissolvables, compressed tobacco, and emerging products that come on the market during the course ofthis research; and 3) the specific mechanisms by which marketing messages change tobacco- related perceptions, perceived acceptability ofthe product, and tobacco use behaviors. Prospective, longitudinal studies using frequent assessments and comprehensive measures of tobacco use, perceptions and marketing are needed to provide specific scientific evidence about how marketing shapes decisions to use and stop using different tobacco products. This information will inform FDA regulation ofthe marketing and promotion of conventional, new, and emerging tobacco products. This study will fill gaps in the science base by developing and testing a comprehensive model concerning the relationships among pro- and anti- tobacco marketing messages, perceptions of tobacco risks and benefits, perceived product acceptability, and patterns of tobacco use among adolescents and young adults. We will address these gaps and develop and test our model by using a longitudinal cohort design with a sample of 1,000 ninth graders followed through high school and another sample of 1,000 twelfth graders followed into young adulthood to 1) determine adolescents' and young adults' perceptions of risk for disease, addiction, and death; acceptability; and benefits of using conventional, new, and emerging tobacco products that come on the market during the course ofthis research; 2) determine the predictive relationships among perceptions of tobacco-related risks, benefits, and acceptability of tobacco products, and the onset, continuation, cessation, relapse, switching, and dual use of tobacco products; and 3) identify contextual factors (exposure to pro-tobacco media, anti- tobacco media, warning labels, and smoking images in the media and on the Internet) that influence perceptions of risks, benefits, acceptability, and subsequent tobacco use. RELEVANCE (See instructions^; The proposed project will make novel and important contributions to our understanding of how tobacco marketing impacts risk perceptions and ultimately tobacco use among adolescents and young adults. There are currently no prospective, longitudinal studies using theoretically informed data collection tools that can identify predictive relationships among perceptions, pro-tobacco marketing, anti-tobacco messages, warning labels, and patterns of adolescents' and young adults' tobacco use. The proposed study will explore smoking patterns and predictors in a critical but understudied age cohort: young adults. .